Level luffing crane

ABSTRACT

An articulated crane has an inner boom pivoted on a supporting base, an outer boom pivotally mounted on the inner boom, and a pair of hydraulic cylinder assemblies, one for moving each of the booms, respectively. The hydraulic cylinder assemblies may be interconnected when desired to coordinate their simultaneous movement, and they are so positioned with respect to the boom pivots that their coordinated movement causes the outer end of the outer boom to travel substantially horizontally.

United States Patent 11 1 Suverkrop 1 May 20, 1975 l LEVEL LUFFING CRANEInventor: Don Suverkrop, Bakersfield. Calif.

[73} Assignee: Hopper, lnc., Bakersfield, Calif.

1 Filed: Aug. 26, 1970 App]. No.: 66,969

Related U.S. Application Data [63] Continuation-impart of Ser. No,779,403, Nov. 27,

[52] U.S. C1. 212/35; 212/59; 212/144 [51] Int. Cl. B66c 23/54 [58]Field of Search 212/8, 35,55, 59, 144

[56] References Cited UNITED STATES PATENTS 3,244,292 4/1966 Elliott212/59 3,265,219 8/1966 Sundin.... 212/35 3,268,092 8/1966 Hainerm.212/59 3,352,441 11/1967 Alden .,212/8 3,543,944 12/1970 Woodside 212/35FOREIGN PATENTS OR APPLlCATIONS United Kingdom 212/35 1,052,658 3/1959Germany 212/35 1,125,981 9/1968 United Kingdom 212/59 6,618,469 7/1968Netherlands 212/35 588,899 6/1947 United Kingdom 212/35 Primary Examinerlames B. Marbert Attorney, Agent, or Firm-Lyon and Lyon [57] ABSTRACT Anarticulated crane has an inner boom pivoted on a supporting base, anouter boom pivotally mounted on the inner boom, and a pair of hydrauliccylinder assemblies, one for moving each of the booms, respectively. Thehydraulic cylinder assemblies may be interconnected when desired tocoordinate their simultaneous movement, and they are so positioned withrespect to the boom pivots that their coordinated movement causes theouter end of the outer boom to travel substantially horizontally.

15 Claims, 8 Drawing Figures SHEET 10F S PATENTEI] HAY 2 01975PATENTEDHAYZOIHTS SHEET 2 BF 5 INVENTOR DON 5UI EFKEOP 6; fi g PATENTED3,884,359

INVEN'IOR Dd/V SUI/665E01 ATTOZ/WSVS PATENTED 3,884,359

SHEET R []F 5 INVENTOR DO/\/ 56/ l EEKEOP LEVEL LUFFING CRANE This is acontinuation-in-part of my copending application Ser. No. 779,403, filedNov. 27, I968 for Level Luffing Crane.

This invention relates to hydraulically operated articulated cranes. Asa type, these cranes have achieved commercial success because of theirsimplicity, flexibility in handling loads in a variety of positions, andeconomical price. Cranes of this type commonly employ a base membermounted on a turntable, an inner boom pivoted to the base member, and anouter boom pivoted to the inner boom. Separate hydraulic cylinderassemblies, one of each boom, are employed.

An important shortcoming of articulated cranes of this type is thedifficulty of moving a load horizontally toward or away from the axis ofthe turntable, because both hydraulic cylinder assemblies must beoperated at the same time, requiring very skillful operation of themanual control levers. Separate operation of each hydraulic cylinderassembly results in the load hook swinging in a vertical arc. Only byskillful operation of both controls at the same time is it possible tocause the load to move horizontally toward or away from the turntableaxis. Such horizontal movement is known as level luffing.

It is an important object of this invention to provide an improvedhydraulically operated articulated crane that retains the advantages ofsimplicity, flexibility and price associated with the general design,but which in addition provides for automatic level luffing when desired.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

FIG. 1 is a side elevation showing a preferred embodiment of myinvention.

FIG. 2 is an end view thereof, partly broken away.

FIG. 3 is a side elevation showing a modified form of the invention.

FIG. 4 is a side elevation showing another modified form of theinvention.

FIG. 5 is a side elevation showing still another modified form of theinvention.

FIG. 6 is a side elevation of a somewhat similar device but which doesnot produce automatic level luff- FIG. 7 is a schematic diagram showinghydraulic connections for the devices of FIGS. 1 and 2.

FIG. 8 is a schematic diagram constituting a modification of a portionof FIG. 7.

Referring to the drawings, the base member 10 is carried on a stationarysupport 1 l by means of a large horizontal bearing assembly 12. An innerboom 13 is pivotally mounted on the base member 10 and 14, and an outerboom 15 is pivotally connected to the inner boom at 16. The firsthydraulic cylinder assembly 17 is operatively positioned between thebase member 10 and the inner boom 13. Thus the outer shell of theassembly 17 is pivoted to the base member 10 at 18, and the piston rodend of the assembly 17 is pivotally connected at 19 to the bracket 20fixed on the inner boom 13. Similarly, the hydraulic cylinder assembly22 is operatively positioned between the inner boom 13 and the outerboom 15. The outer shell of the assembly 22 is pivoted at 23 to thebracket 20 and the piston rod end of the assembly is pivoted at 24 tothe bracket 25 on the outer boom 15. From this description, it will beunderstood that actuation of the hydraulic cylinder assembly 17 servesto swing the inner boom 13 around the pivot 14, and actuation ofhydraulic cylinder assembly 22 serves to swing the outer boom 15 aroundthe pivot 16.

An hydraulically operated winch 27 of conventional design may beconveniently mounted on the inner boom 13' near the pivot 14. A cable 28extending from the winch 27 passes over the pulley or sheave 29 whichmay be coaxial with the pivot 16. The cable then passes over the sheave30 mounted at the swinging end of the outer boom 15, and this cable 28pendantly supports the load hook 31. Operation of the hoist 27 to windup the cable 28 serves to lift the load hook 31.

An hydraulic motor 33 mounted on the base member 10 is gear connected tothe satisfactory support 11 in order to swing the entire crane assemblyin either direction above the axis of the bearing 12.

At the operators console 34 a plurality of manually operated controllevers 35 are provided. One of these levers serves to operate theturntable motor 33, another operates the hydraulic cylinder assembly 17,another operates the hydraulic cylinder assembly 22, and the fourthlever hydraulically interconnects the hydraulic cylinder assemblies 17and 22 to coordinate their simultaneous movement, so that theload-supporting hook 31 travels substantially horizontally toward oraway from the turn-table axis. This fourth lever thus provides forautomatic lever luffing. The hydraulic diagram of FIG. 7 shows how thishydraulic interconnection may be accomplished. Two hydraulic pumps 37and 38 are driven from the same prime mover 39 mounted on the basemember 10. The low volume pump 37 is connected through filter 40 todeliver hydraulic fluid under pressure to the valve 41 for the turntablemotor and to the valve 42 for level luffing, described below. The highvolume pump 38 delivers hydraulic fluid under pressure through thefilter 43 to the valve 44 for the hydraulic cylinder assembly 17, and tothe valve 45 for the hydraulic cylinder assembly 22, and to the valve 46for the hydraulically operated hoist 27. Spring loaded relief valves 48and 49 return hydraulic fluid to the central reservoir or sump, when theunit pressure exceeds the predetermined maximum. Other relief valves 50and 51 are provided for the same purposes.

Each of the manually operable valves 41, 42, 44, 45 and 46 is shown inits intermediate blocking position in which no flow occurs to or fromits respective work member. When the valve 44 is manually depressed,hydraulic fluid under pressure isdelivered from line 53 to line 54, andline 55 to the rod end port 56 of the hydraulic cylinder assembly 17,thereby retracting the piston rod 17r. Hydraulic fluid in the lowerportion of the assembly 17 passes out through the piston end port 57 andline 58 to the check valve 59. This check valve 59 is opened by pressurein the lines 55 and 60 from the pump 38, thereby allowing hydraulicfluid to pass from the line 58 through lines 63, 64 and 65 and backthrough valve 44.. Similarly, manual movement of the valve 44 to anupper position connects line 53 with line 65 so that hydraulic fluidunder pressure passes through lines 64 and 63, check valve 59, line 58and port 57 to cause extension of the piston rod 17r. Hydraulic fluid inthe rod end of the assembly 17 passes out through lines 55 and 54 andthrough the valve 44 to the line 66. The valve 44 is mechanicallyconnected for operation by one of the console levers 35.

In a similar fashion, downward movement of the manually operable valve45 delivers hydraulic fluid under pressure from line 66 through lines 68and 69 to the rod end port 70 of the hydraulic cylinder assembly 22.Hydraulic fluid below the piston escapes through piston end port 71,check valve 72 (held open by pres sure in line 73) and line 74 back tovalve 45. Upward movement of the valve 45 reverses the flow to causeupward movement of the piston rod 22r.

The valve 46 may be moved in either direction to cause operation of thehoist 27 to wind up or pay out the cable 28. Similarly, the valve 41 maybe moved in either direction to pressurize one of the lines 75 or 76 andcause return flow through the other line for the purpose of causing theturntable motor 33 to operate in either direction, as desired.

The level luffing valve 42 has three positions. In the center positionillustrated in FIG. 7, no flow takes place through the valve. When thevalve 42 is moved to the right, the pressurized line 77 from the pump 37is connected to lines 78 and 55 leading to port 56. Back pres sure inthe line 77 acts through line 62 to cause the pilot valve 79 to connectline 63 to line 74 through interconnecting line 61. The back pressure inline 55 acts through line 60 to open check valve 59. Accordingly,hydraulic fluid passes from port 57 through lines 63 and 61, pilot valve79 and line 74 into port 71. The hydraulic cylinder assemblies 17 and 22are so proportioned that they require the same volume of hydraulic fluidduring their respective level luffing strokes. Accordingly, hydraulicfluid is simply transferred from assembly 17 to assembly 22 so that, asthe rod l7r retracts, the rod 22r is extended. The inner boom 13 andouter boom move from the full line position A shown in FIG. 1 to thephantom line position shown at B. Because of the transfer of hydraulicfluid during this operation, the path of the load-supporting hook 31 isshown by the line 81. While this path as shown by the line 81 is notprecisely horizontal, it is near enough for commercial purposes and isreferred to hereinafter as being substantially horizontal. In the fullyretracted position shown at B in FIG. 1, the hydraulic cylinder assembly17 is fully extended and the hydraulic cylinder assembly 22 is fullyretracted. The intermediate position C illustrates independent actioncapability apart from level luffing between positions A and When it isdesired to cause level luffing of the loadsupporting book 31 in theother direction, that is, away from the axis of the turntable, the valve42 is moved to the left, as shown in FIG. 7. This serves to connect thepressure line 77 from the pump 37 to the line 81 and line 69 leading toport 70. This causes piston rod 22r to move downward. Hydraulic fluidpasses out through port 71 and through check valve 72 which is held openby back pressure in the line 73. The hydraulic fluid then passes throughthe pilot valve 79 held by back pressure in lines 77 and 62 and thenpasses through line 61 and 63 to port 57 in the assembly 17.Accordingly, the piston rod l7r moves upward. The booms l3 and 15 moveback from the position shown at B to the solid line position A, all asshown in FIG. 1.

In the device shown in FIGS. 1 and 2, the dimensions of the cylinderassemblies 17 and 22 are chosen so that the total volume of oildischarged from cylinder assembly 22 is the same as that received by thecylinder assembly 17 (and vice versa) during the level luffing stroke.Also, at any given instant along the level luffing traverse, the unitpressure is substantially the same in these cylinder assemblies 17 and22 because of the moment arm relationship of load and hydrauliccylinders. When they are interconnected relatively little additionalpressure is required to cause a transfer of fluid from one cylinderassembly to the other and thus an articulating movement of the arms 13and 15 results, which produces a level luffing of the load. Because thepressure and incremental volume released from one cylinder at anyinstant is so nearly equal to that expended in the other, the traversingmovement is accomplished without the addition or release or work. Suchmovement can only be horizontal. Technically speaking, from physicalprinciples, no work is performed on a load moving horizontally,neglecting friction and accelerations.

In order to achieve the level luffing operation, the angle X between thebooms at the extended position is substantially less than and this angledecreases as the load is moved inward in the level luffing operationuntil the minimum angle Y is reached in the fully retracted position. Inthe form of the invention shown in FIGS. 1 and 2, the effective leverarm of the hydraulic cylinder 22 changes very little from the value L atthe extended position A as compared to the value L at the retractedposition B. The hydraulic cylinder assembly 17 has its maximum lever armL, at the extended position A and this lever arm decreases to theminimum value L at the retracted position B. BThis relationship of theeffective length of the lever arms of the hydraulic cylinder assembliesin the extended position A and the retracted position B produces thelevel luffing action, as shown by the following analysis:

To have level luffing, the arrangement and sizing of parts and cylindersmust be such that the release of work from one cylinder assembly mustequal that expended in the other.

In the arrangement of FIG. 1, when cylinders of equal volume are used,to obtain the equal work relationship the cylinder pressures must beequal to one another at any point in the transverse. If, at eachincrement of displacement along the traverse, the work is balanced, thetraverse is level. If all other increments are balanced, then the totaltraverse is level. Expressed algebraically:

dv P dv P Therefore where dv small volume of fluid transferred at somepoint during the level luffing traverse.

P the pressure in cylinder 17 P the pressure in cylinder 22 at that samepoint in the traverse.

To develop the necessary geometrical relationships to producesubstantial level luffing, assume the pressures in both cylinderassemblies are equalized between them at either end of the traverse. Thefollowing derivation provides the relative change in cylinder momentarms that must transpire during a given traverse.

Taking the summation of moments about the pivot 16, when the booms arein the extended position:

Fd1 P 14114 where F is the force or weight acting on the outer end ofthe boom d is the distance through which the force F acts;

P is the unit pressure of fluid in the hydraulic cylinder 22 at extendedposition;

A is the area of the piston in the assembly 22 against which thishydraulic pressure acts;

L is the effective lever arm of the assembly 22 at extended position.

Solving for P Fd, T

Taking the summation of moments about the pivot 14:

where P is the unit pressure of the fluid in the assembly 17; A is thearea-of the piston in the assembly 17 which is subjected to thishydraulic pressure;

L is the effective lever arm of the assembly 17. Solving for P Equating(l) and (2), because the unit hydraulic pressure in each of theassemblies 22 and 17 is the same:

Solving for D Fdz PrA1l2 where P, is the unit pressure in the hydrauliccylinder assembly 22 at retracted position;

I is the effective lever arm of the assembly 22 in retracted position.

Solving for P Allz (4) Taking the summation of moments about the pivot14:

F D P A L Solving for P,:

FD P,= A214 Equating (4) and (5) because the unit hydraulic pressure isthe same in each of the assemblies 22 and 17:

F11 F1) A112 A214 Solving for D 1214 1121 .14 A,I2F M2 (6) From theforegoing:

Stated in other words, in order to achieve level luffing with the FIG. 1device, and with hydraulic pressure in the assembly 22 substantiallyequal to that in the assembly 17 at each point along the level luffingtraverse, the assembly 17 must be mounted so that its effective leverarm L, at the extended position A of the booms is proportional to theoverall horizontal reach D of the booms at extended position, while theeffective lever arm L of the assembly 17 at retracted position B isproportional to the horizontal reach D of the booms at retractedposition. Accordingly, the ratio of the effective lever arm of thesecond hydraulic cylinder assembly 22 to the effective lever arm of thefirst hydraulic cylinder assembly 17 increases as the booms move awayfrom extended position toward retracted position.

In the device of FIGS. 1 and 2 but using cylinders of unequaldisplacement, the flow proportioning device 200-201 of FIG. 8 isinterposed, to provide a related proportioning of fluid betweencylinders 17 and 22.

Again, a relation of equal work transfer requires at any instant oflevel luffing that:

(111 X P 7 dv X P where dv small volume of fluid transferred to or fromcylinder 17 at an instant;

dv small fluid volume transferred to or from cylinder 22 at the sameinstant;

P fluid pressure within cylinder 17 at instant of fluid transfer;

P fluid pressure within cylinder 22 at instant of fluid transfer. But

V 9 (does not equal) V therefore Taking summation of moments about 16 inretracted dv (ii position: But an equal number of volume increments aredishtt'll llff t'- placed In each cylinder durmgt e o a eve u mg I'd 1 222r M2 verse. 5

Therefore Fd ndVy V17 P22 A112 and ndvzg V Taking summation of momentsabout 14in retracted where position:

n number of volume increments and ndv" P" ndvzz P22 2M": Fl): kPgg -AzLztherefore FD,

where V volume cyl l7 Equating (l4) and (15) V volume cyl 22 Therefore,to have an equal work relation in each cylinder the product of thevolume of one cylinder l F02 times its pressure at a given instant mustequal the A214, product of the volume of the other cylinder times its Sl f D pressure at the same instant. o vmg or 2 From the equation (10)then the pressures are related d A L K l 2 I) d,A L,k d A l k P17: P22D2 l l A112 For convenience let since d is substantially the same as daccordingly D L l V l 2 Vi: D2 11 X II M then Therefore in the case of acrane with cylindersof unequal volume the stroke and area relationshipsof the 11 k 22 0 linders must be such that 3 With this pressurerelationship take moments atea'ch VHF": VHF end of the traverse todevelop the desired geometric re- 40 l lationship. and the geometricrelation of Taking sumrriation'of moments about 16 in extended position:I D1 I; X 12 2 4 l |s l ZZJ I I must also exist.

PM (I I) If it is desired to refine the path of movement of theload-supporting hook 31 during the level luffing operation so that itmore closely approaches an exact horizontal line, a cam-and-followerdevice may be employed for modifying the rate of transfer of hydraulicfluid between the assemblies 17 and 22. As shown in 2M: FDl kpmAzLl thedrawings, this cam-and-follower device comprises a cam 84 fixed to theinner boom 13, together with a p 12 follower roller 85 held in contactwith the surface of 2 the cam 84. The follower roller 85 is mounted onthe Taking summation of moments about 14 in extended 50 position:

Equating (l 1) and (12) extending rod 86 of the hydraulic cylinderassembly 87 and the space below the piston is connected by line 87a tothe line 74 to the pilot valve 79. In and out move- F11. FD ment of therod 86 under action of the follower roller l 2 1 I 85 transfershydraulic fluid into and out of the line con- I taining the pilot valve79, in accordance with the angusol i g for 1 lar position of the innerboom 13. The varying volume of hydraulic fluid causes variations in therelative movement of the piston rods 17r and 22r to minimize deviationof the path of the load-supporting hook 31 from a true horizontal line.

In the modified form of the invention shown in FIG. 3 of the drawings,the parts are generally similar to those previously described, exceptthat the outer boom 15a is provided with an extension member 100telescopically mounted thereon. The stationary support 1111, turntablebearing 12a, base member a, inner boom 13a and pivotal connections 14aand 16a are all similar to corresponding parts previously described. Thesame is true of the hydraulic cylinder assemblies 17a and 22a and theirrespective pivotal connections 18a, 19a, and 23a, 24a.

A third hydraulic cylinder assembly 101 is provided for extending orretracting the extension member 100 with respect to the outer boom a. Asheave 102 is mounted at the projecting end of the extension 100 toreceive a load-supporting cable, not shown.

The same hydraulic circuits previously described may be employed forproviding independent operation of the hydraulic cylinder assemblies 17aand 22a, or for providing coordinated action thereof for accomplishinglevel luffing. The phantom line position at A in FIG. 3 shows the boomsin retracted position, while the phantom line position at B shows thebooms in a folded position for transport. In this latter position, theouter boom 15a underlies the position of the inner boom 1311.

It will be observed that the positions of the hydraulic cylinderassemblies 220 and 17a with respect to the booms 15a and 13a and withrespect to the stationary support 10a are similar to those positions setforth in detail above with respect to the form of the invention shown inFIGS. 1 and 2.

The modified form of the invention shown in FIG. 4 has a base 10bpivotally supporting a first boom 13b at 14b, and a second boom 15bpivotally supported on the boom 13b at 16b. The first boom 13b is movedby the hydraulic cylinder assembly 17b and the second boom 15b is movedby the hydraulic cylinder assembly 22b. The hydraulic connections andthe controls are the same as previously described. In this form of theinvention, however, the hydraulic cylinder assembly 17b has asubstantially constant effective lever arm L and L while the hydrauliccylinder assembly 22b has a short effective lever arm I, in the extendedposition of the booms which increases to a long effective lever arm 1 inthe retracted position. As shown by the mathematical analysis set forthin detail above:

tive lever arm. Thus, the effective lever arm L, of the assembly 17:decreases to L as the booms are moved from extended position toretracted position, while the effective lever arm of the assembly 22c 1increases to 1 during the same movement of the booms. Thus, oneeffective lever arm increases as the other decreases, and vice versa. Solong as the relationship of the parts is such that the relationship ofequation (8) apply, substantial level luffing is achieved.

However, asequation (8) indicates, substantial level luffing action isnot achieved if the boom-operating hydraulic cylinder assemblies bothhave substantially constant effective lever arms, that is, when L, L and=1 Moreover, level luffing is not achieved in other designs in which oneor both of the hydraulic cylinder assemblies have effective lever armswhich change from extended position to retracted position, unless theratio of the effective lever arm of the second hydraulic cylinderassembly to that of the first hydraulic cylinder assembly increases asthe booms move away from extended position toward retracted position.This is shown in the diagram of FIG. 6. In this construction, thehydraulic cylinder assembly 220. operating the second boom has aneffective lever arm which decreases from I, when extended to 1 whenretracted. Also, the hydraulic cylinder assembly 17d operating the firstboom 13d has an effective lever arm which decreases from L, whenextended to L when retracted. The arched curved line 81d whichshows themotion of the outer end of the second boom 15d is substantially higherat the center than it is at either end. Substantial level luffing actionis not obtained because the required ratio of effective lever arms isnot achieved.

The modification of the hydraulic diagram, as shown in FIG. 8, is foruse when the hydraulic cylinder assemblies 17 and 22 are dimensioned sothat they displace different volumes of oil during the level luffingstroke. This may be desirable in some cases for best economical use ofmaterials. In such case, means are provided for proportioning the rateof flow of oil to produce the desired coordination of movement of thepiston rods. Thus, two positive displacement pumps 200 and 201 areemployed, mechanically connected by shaft 202. Hydraulic fluid leavingcylinder assembly 22 through port 71 during the level luffing strokepasses through valve 79 and is metered through pump 200 to tank. Thiscauses pump 201 to draw oil from the tank and discharge it through checkvalve 59 into the cylinder 17 through port 57. The capacity of the pumpsare proportional to the displacement volumes-of the cylinders; if thecylinder 22 has twice the displacement volume as cylinder 17 during thelevel luffing stroke, then pump 200 is proportioned to have twice thecapacity of the pump 201. In a similar fashion, when pump 201 metershydraulic fluid from cylinder 17, the shaft-connected pump 200 drawsfluid from the tank and discharges it through check valve 72 intocylinder 22 through port 71.

Having fully described my invention, it is to be understood that I amnot to be limited to the details herein set forth but that my inventionis of the full scope of the appended claims.

I claim:

1. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base :member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an are on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said second assemblydefining a second effective lever arm with respect to the pivotalmounting of the outer boom, said booms being movable in a traverse froman extended position in which the inner boom inclines upward on one sideof the vertical and the outer boom extends further to the same sidethereof and the angle between the booms being less than 180 degrees, toa retracted position in which the inner boom inclines upward on theother side of the vertical and the outer boom extends to the firstmentioned side thereof, the positions of the booms, hydraulic cylinderassemblies, and pivotal connections being such that where:

D, horizontal reach of the booms when extended D horizontal reach of thebooms when retracted L effective lever arm of said first hydrauliccylinder assembly extended L effective lever arm of said first hydrauliccylinder assembly retracted l, effective lever arm of said secondhydraulic cylinder assembly extended I effective lever arm of saidsecond hydraulic cylinder assembly retracted the cylinder assembliesbeing sized according to the relation where:

P, unit pressure in first hydraulic cylinder assembly at a given instantP unit pressure in second hydraulic cylinder assembly at the sameinstant V, displacement volume of the first hydraulic cylinder assemblyduring said traverse V displacement volume of the second hydrauliccylinder assembly during said traverse and hydraulic meansinterconnecting said hydraulic cylinder assemblies to coordinate theirsimultaneous action to cause the outer end of the outer boom to movesubstantially horizontally and above the level of said pivot means.

2. The device set forth in claim 1 in which =1 3. The device set forthin claim 1 in which the means interconnecting the hydraulic cylinderassemblies is such that as one retracts the other extends, and viceversa.

4. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an are on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said assembly defining asecond effective lever arm with respect to the pivotal mounting of theouter boom, said booms being movable in a traverse from an extendedposition in which the inner boom inclines upward on one side of thevertical and the outer boom extends further to the same side thereof andthe angle between the booms being less than to a retracted position inwhich the inner boom inclines upward on the other side of the verticaland the outer boom extends to the first mentioned side thereof, theratio of the effective lever arm of the second hydraulic cylinderassembly to the effective lever arm of the first hydraulic cylinderassembly increasing as the booms move along the traverse away fromextended position toward retracted position, and means interconnectingsaid hydraulic cylinder assemblies to coordinate their simultaneousaction so that one retracts as the other extends, and vice versa, tocause the outer end of the outer boom to move substantially horizontallyand above the level of said pivot means.

5. The combination set forth in claim 4 in which the hydraulic cylinderassemblies are proportioned so that they require the same volume ofhydraulic fluid to complete their full strokes, respectively.

6. The combination set forth in claim 4 in which each hydraulic cylinderassembly has a piston end, and wherein said hydraulic means includes avalvecontrolled passage connecting the piston ends of both hydrauliccylinder assemblies, for transfer of hydraulic fluid from one to theother.

7. The combination set forth in claim 4 in which an extension boom istelescopically mounted on said outer boom, and sheave means at one endof said extension boom.

8. The combination set forth in claim 7 in which full retraction of thesecond hydraulic cylinder assembly serves to swing the outer boom to afolded position under the inner boom.

9. The combination set forth in claim 4 in which where P, unit pressurein first hydraulic cylinder assembly at a given instant; P unit pressurein second hydraulic cylinder assembly at the same instant; Vdisplacement volume of the first hydraulic cylinder assembly during saidtraverse; V displacement volume of the second hydraulic cylinderassembly during said traverse. 10. An articulated crane, comprising incombination: a base member, an inner boom, pivot means mounting saidinner boom on the base member, an outer boom pivotally mounted on theinner boom, means including a first extensible hydraulic cylinderassembly for swinging said inner boom with respect to said base memberin an are on both sides of the vertical position, means including asecond extensible hydraulic cylinder assembly for independently swingingsaid outer boom with respect to said inner boom, said booms beingmovable between an extended position and a retracted position, inextended position the inner boom including upward on one side of thevertical and the outer boom extending further to the same side thereof,and the angle between the booms being less than 180, in retractedposition the inner boom inclining upward on the other side of thevertical and the outer boom extending to the first mentioned sidethereof, the effective lever arm of the first hydraulic cylinderassembly remaining substantially constant, and the effective lever armof the second hydraulic cylinder assembly increasing as the booms moveaway from extended position toward retracted position, and hydraulicmeans interconnecting said hydraulic cylinder assemblies to coordinatetheir simultaneous action to cause the outer end of the outer boom tomove substantially horizontally and above the level of said pivot means.

11. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an arc on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said second assemblydefining a second effective lever arm with respect to the pivotalmounting of the outer boom, said booms being movable between an extendedposition and a retracted position, in extended position the inner boominclining upward on one side of the vertical and the outer boomextending further to the same side thereof, and the angle between thebooms being less than 180, in retracted position the inner boominclining upward on the other side of the vertical and the outer boomextendingto the first mentioned side thereof, the effective lever arm ofthe second hydraulic cylinder assembly remaining substantially constant,and the effective lever arm of the first hydraulic cylinder assemblydecreasing as the booms move away from extended position towardretracted position, and hydraulic means interconnecting said hydrauliccylinder assemblies to coordinate their simultaneous action to cause theouter end of the outer boom to move substantially horizontally and abovethe level of said pivot means.

12. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for swinging said inner boom withrespect to said base member in an arc on both sides of the verticalposition, means including a second extensible hydraulic cylinderassembly for independently swinging said outer boom with respect to saidinner boom, said booms being movable between an extended position and aretracted position, in extended position the inner boom inclining upwardon one side of the vertical and the outer boom extending further to thesame side thereof, and the angle between the booms being less than inretracted position the inner boom inclining upward on the other side ofthe vertical and the outer boom extending to the first mentioned sidethereof, the effective lever arm of the second hydraulic cylinderassembly progressively increasing, and the effective lever arm of thefirst hydraulic cylinder assembly progressively decreasing as the boomsmove away from extended position toward retracted position, andhydraulic means interconnecting said hydraulic cylinder assemblies tocoordinate their simultaneous action to cause the outer end of the outerboom to move substantially horizontally and above the level of saidpivot means.

13. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for inde pendently swinging saidinner boom with respect to said base member in an are on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said second assemblydefining a second effective lever arm with respect to the pivotalmounting of the outer boom, said booms being movable in a traversebetween an extended position and a retracted position, in extendedposition the inner boom inclining upward on one side of the vertical andthe outer boom extending further to the same side thereof, and the anglebetween the booms being less than 180, in retracted position the innerboom inclining upward on the other side of the vertical and the outerboom extending to the first mentioned side thereof, and the anglebetween the booms being less than at extended position, the ratio of theeffective lever arm of the second hydraulic cylinder assembly to theeffective lever arm of the first hydraulic cylinder assembly increasingas the booms move away from extended position toward retracted position,whereby substantially equal pressures are induced in said hydrauliccylinder assemblies at each point along said traverse, and meansinterconnecting said hydraulic cylinder assemblies to coordinate theirsimultaneous action to cause the outer end of the outer boom to movesubstantially horizontally and above the level of said pivot means.

14. The combination set forth in claim 13 in which the hydrauliccylinder assemblies displace different volumes of fluid in theirrespective strokes between extended position and retracted position.

15. The combination set forth in claim 14 in which two positivedisplacement pumps are provided, one connected to each hydrauliccylinder assembly, respectively, the pumps being mechanically connectedfor dependent rotation.

UNITED STATES PATENT OFFICE @ERTEFIQATE 0F CORREQTION PATENT NO.3,884,359

DATED May 20, 1975 INVENTOMS) Don Suverkrop It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown heiow:

Col, 2 line 15 "satisfactory" should read stationary- Col. 4, line 13,"or work" should read -of work-- Col. 4, line 30, B. 'B" should read--"B.

Col. 4, line 42, "transverse" should read traverse Col. 7, line 29, theformula 17 22 2 should read C01. 7, last line, the formula "D dlAZLlk"ShOuld A Ql read --D Col. 8, line 5, the formula should read:

Signed and gcaled this nineteenth Day of August 1975 [SEAL] Arrest:

RUTH C. MASON c-illrslmg Officer C. MARSHALL DANN (rmrmrssiunvruj'lau'nls and Trademarks

1. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an arc on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said second assemblydefining a second effective lever arm with respect to the pivotalmounting of the outer boom, said booms being movable in a traverse froman extended position in which the inner boom inclines upward on one sideof the vertical and the outer boom extends further to the same sidethereof and the angle between the booms being less than 180 degrees, toa retracted position in which the inner boom inclines upward on theother side of the vertical and the outer boom extends to the firstmentioned side thereof, the positions of the booms, hydraulic cylinderassemblies, and pivotal connections being such that
 2. The device setforth in claim 1 in which l2 l1.
 3. The device set forth in claim 1 inwhich the means interconnecting the hydraulic cylinder assemblies issuch that as one retracts the other extends, and vice versa.
 4. Anarticulated crane, comprising in combination: a base member, an innerboom, pivot means mounting said inner boom on the base member, an oUterboom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an arc on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said assembly defining asecond effective lever arm with respect to the pivotal mounting of theouter boom, said booms being movable in a traverse from an extendedposition in which the inner boom inclines upward on one side of thevertical and the outer boom extends further to the same side thereof andthe angle between the booms being less than 180*, to a retractedposition in which the inner boom inclines upward on the other side ofthe vertical and the outer boom extends to the first mentioned sidethereof, the ratio of the effective lever arm of the second hydrauliccylinder assembly to the effective lever arm of the first hydrauliccylinder assembly increasing as the booms move along the traverse awayfrom extended position toward retracted position, and meansinterconnecting said hydraulic cylinder assemblies to coordinate theirsimultaneous action so that one retracts as the other extends, and viceversa, to cause the outer end of the outer boom to move substantiallyhorizontally and above the level of said pivot means.
 5. The combinationset forth in claim 4 in which the hydraulic cylinder assemblies areproportioned so that they require the same volume of hydraulic fluid tocomplete their full strokes, respectively.
 6. The combination set forthin claim 4 in which each hydraulic cylinder assembly has a piston end,and wherein said hydraulic means includes a valve-controlled passageconnecting the piston ends of both hydraulic cylinder assemblies, fortransfer of hydraulic fluid from one to the other.
 7. The combinationset forth in claim 4 in which an extension boom is telescopicallymounted on said outer boom, and sheave means at one end of saidextension boom.
 8. The combination set forth in claim 7 in which fullretraction of the second hydraulic cylinder assembly serves to swing theouter boom to a folded position under the inner boom.
 9. The combinationset forth in claim 4 in which P1V1 Congruent P2V2 where P1 unit pressurein first hydraulic cylinder assembly at a given instant; P2 unitpressure in second hydraulic cylinder assembly at the same instant; V1displacement volume of the first hydraulic cylinder assembly during saidtraverse; V2 displacement volume of the second hydraulic cylinderassembly during said traverse.
 10. An articulated crane, comprising incombination: a base member, an inner boom, pivot means mounting saidinner boom on the base member, an outer boom pivotally mounted on theinner boom, means including a first extensible hydraulic cylinderassembly for swinging said inner boom with respect to said base memberin an arc on both sides of the vertical position, means including asecond extensible hydraulic cylinder assembly for independently swingingsaid outer boom with respect to said inner boom, said booms beingmovable between an extended position and a retracted position, inextended position the inner boom including upward on one side of thevertical and the outer boom extending further to the same side thereof,and the angle between the booms being less than 180*, in retractedposition the inner boom inclining upward on the other side of thevertical and the outer boom extending to the first mentioned sidethereof, the effective lever arm of the first hydraulic cylinderassembly remaining substantially constant, and the effective lever armof the second hydraulic cylinder assembly increasing as the booms moveaway from extended position toward retracted position, and hydraulicmeans interconnecting said hydraulic cylinder assemblies to coordinatetheir simultaneous action to cause the outer end of the outer boom tomove substantially horizontally and above the level of said pivot means.11. An articulated crane, comprising in combination: a base member, aninner boom, pivot means mounting said inner boom on the base member, anouter boom pivotally mounted on the inner boom, means including a firstextensible hydraulic cylinder assembly for independently swinging saidinner boom with respect to said base member in an arc on both sides ofthe vertical position, said assembly defining a first effective leverarm with respect to said pivot means, means including a secondextensible hydraulic cylinder assembly for independently swinging saidouter boom with respect to said inner boom, said second assemblydefining a second effective lever arm with respect to the pivotalmounting of the outer boom, said booms being movable between an extendedposition and a retracted position, in extended position the inner boominclining upward on one side of the vertical and the outer boomextending further to the same side thereof, and the angle between thebooms being less than 180*, in retracted position the inner boominclining upward on the other side of the vertical and the outer boomextending to the first mentioned side thereof, the effective lever armof the second hydraulic cylinder assembly remaining substantiallyconstant, and the effective lever arm of the first hydraulic cylinderassembly decreasing as the booms move away from extended position towardretracted position, and hydraulic means interconnecting said hydrauliccylinder assemblies to coordinate their simultaneous action to cause theouter end of the outer boom to move substantially horizontally and abovethe level of said pivot means.
 12. An articulated crane, comprising incombination: a base member, an inner boom, pivot means mounting saidinner boom on the base member, an outer boom pivotally mounted on theinner boom, means including a first extensible hydraulic cylinderassembly for swinging said inner boom with respect to said base memberin an arc on both sides of the vertical position, means including asecond extensible hydraulic cylinder assembly for independently swingingsaid outer boom with respect to said inner boom, said booms beingmovable between an extended position and a retracted position, inextended position the inner boom inclining upward on one side of thevertical and the outer boom extending further to the same side thereof,and the angle between the booms being less than 180*, in retractedposition the inner boom inclining upward on the other side of thevertical and the outer boom extending to the first mentioned sidethereof, the effective lever arm of the second hydraulic cylinderassembly progressively increasing, and the effective lever arm of thefirst hydraulic cylinder assembly progressively decreasing as the boomsmove away from extended position toward retracted position, andhydraulic means interconnecting said hydraulic cylinder assemblies tocoordinate their simultaneous action to cause the outer end of the outerboom to move substantially horizontally and above the level of saidpivot means.
 13. An articulated crane, comprising in combination: a basemember, an inner boom, pivot means mounting said inner boom on the basemember, an outer boom pivotally mounted on the inner boom, meansincluding a first extensible hydraulic cylinder assembly forindependently swinging said inner boom with respect to said base memberin an arc on both sides of the vertical position, said assembly defininga first effective lever arm with respect to said pivot means, meansincluding a second extensible hydraulic cylinder assembly forindependently swinging said outer boom with respect to said inner boom,said second assembly defining a second effective leveR arm with respectto the pivotal mounting of the outer boom, said booms being movable in atraverse between an extended position and a retracted position, inextended position the inner boom inclining upward on one side of thevertical and the outer boom extending further to the same side thereof,and the angle between the booms being less than 180*, in retractedposition the inner boom inclining upward on the other side of thevertical and the outer boom extending to the first mentioned sidethereof, and the angle between the booms being less than at extendedposition, the ratio of the effective lever arm of the second hydrauliccylinder assembly to the effective lever arm of the first hydrauliccylinder assembly increasing as the booms move away from extendedposition toward retracted position, whereby substantially equalpressures are induced in said hydraulic cylinder assemblies at eachpoint along said traverse, and means interconnecting said hydrauliccylinder assemblies to coordinate their simultaneous action to cause theouter end of the outer boom to move substantially horizontally and abovethe level of said pivot means.
 14. The combination set forth in claim 13in which the hydraulic cylinder assemblies displace different volumes offluid in their respective strokes between extended position andretracted position.
 15. The combination set forth in claim 14 in whichtwo positive displacement pumps are provided, one connected to eachhydraulic cylinder assembly, respectively, the pumps being mechanicallyconnected for dependent rotation.